Recently, in an optical system used in a camera and the like, there is a tendency that a most object side lens group is large-sized in accordance with angle of view being enlarged and an aperture being enlarged. Because of this tendency, light outside of an effective flux of a lens is made incident on the most object side lens and deteriorates optical performance, and therefore an optical system taking any measures for avoiding this has been proposed. For example, Japanese Patent Application Laid-open No. 2001-296465 should be referred.